res_musiconhold.c: Fix format ref leak when parsing MOH config class.

Change-Id: Ica8e8e2ce7604c2c61ec55bef07dc675361d2ea5

res/res_musiconhold.c

@@ -1433,6 +1433,7 @@ static int local_ast_moh_start(struct ast_channel *chan, const char *mclass, con
 				else if (!strcasecmp(tmp->name, "sort") && !strcasecmp(tmp->value, "alpha")) 
 					ast_set_flag(mohclass, MOH_SORTALPHA);
 				else if (!strcasecmp(tmp->name, "format")) {
+					ao2_cleanup(mohclass->format);
 					mohclass->format = ast_format_cache_get(tmp->value);
 					if (!mohclass->format) {
 						ast_log(LOG_WARNING, "Unknown format '%s' -- defaulting to SLIN\n", tmp->value);
@@ -1765,6 +1766,7 @@ static int load_moh_classes(int reload)
 			} else if (!strcasecmp(var->name, "sort") && !strcasecmp(var->value, "alpha")) {
 				ast_set_flag(class, MOH_SORTALPHA);
 			} else if (!strcasecmp(var->name, "format")) {
+				ao2_cleanup(class->format);
 				class->format = ast_format_cache_get(var->value);
 				if (!class->format) {
 					ast_log(LOG_WARNING, "Unknown format '%s' -- defaulting to SLIN\n", var->value);